Recovery of hydrocarbons



Patented Dec. l17, 1946 RECOVERY on` HypnocAnBoNs Edward `Buddrus and Samuel C. Carney,` Bartles-` ville, Okla., assignors `to Company, a corporationof Phillips Petroleum Delaware Appuuondulyzs, 1941, sera1No.404,0s0

s claims.' (cities-21) This invention relates to the production of vcrude oils and more particularly to `a method of secondary recovery of petroleum oils from `partially depleted oil reservoirs. This invention also relates to methods of preparing undergrOund reservoii's for the storing of light volatile hydrocarbons.

Present day practice in the art of producing petroleum oils from underground reservoirs frequently employs methods of secondary recovery in order to increase the rate of fluid recovery and to drain more effectively the reservoir of its hydrocarbon fluids.' Secondary recovery is usually started when a reservoir has become so depleted of` its lluid that 'the rate of production is deemed uneconomical. Common secondary methods include such as air or gas pressure, recycling and Water flooding. These fluids may be injected into, for example, one centrally located input well' and the increased production. withdrawn from outlying wells, or they may be injected into and increased production withdrawn froml alternately located wells.

`While present day methods of secondaryV recovery aid substantially in the recovery of petroleum iluids,` there y are inherent disadvantages which limit the ultimate oil recovery. For example, when fluids are injected into reservoirs at pressures substantially in excess of the existing reservoir pressure, the injected fluids may flush out the porouslpermeable portions of the formations, leaving large quantities of oil in the less porous. less permeable areas. .When water is injected into a reservoir precipitates and emulsions may form which plug the pores, and the use of air freouentlv causes plugging through` tar, gum

and resin formation and deposition and even paratllndeposition. And,`further, present day secondaryrecoverv methods do not remove all of d the petroleum from the reservoirs.

In the practice of our invention, selected hydrocarbon vapors are'A injected through the well bore into the surrounding partially depleted formation at pressures of the same order as those existing in the formation. The hydrocarbon vapors selected forinjection are such that at reservoir temperatures` and under injection pressures they condense to liquid within the4 pores of said partially depleted formation. Unlike former processes, our invention does not permit channeling of the vapor even in porous and barren areas by the use of forceor pressure because the vapor upon injection condenses and seals the pores with its own condensate. Condensation of these selected hydrocarbons vwithin the pores gives out latent heat and forms a solvent that is wholly miscible with the petroleum oil, lowers the surface 'tension and decreases the viscosity of theresidual petroleum thereby assisting natural drainage into the well bore. In our preferred embodiment, We disclose the use of such'hydrocarbons or hydrocarbon mixtures as propane and butane. The accumulated liquid propane and butane solvent with its charge of residual petroleum is produced from the well by pumping,` separated into essentially a crude oil fraction, and a recycle fraction comprising essentially vaporous propane and butane. Our method requires only a .minimum of material from outside sources, because the use of this propane and butane solvent' lscyclic and the solvent supply increases as the ,operation progresses from the propane and butane occurring in the formation oil. And, when the secondary recovery operation iscompleted, the solvent used may be essentially completely recovered and the formation is then in excellent condition to serve as a storage reservoir for light y petroleum products, such asbut'ane and/or pro` pane, which under presentoperating conditions are frequently not conserved due to the danger and impracticability involved in the storage of these materials in large quantities in pressure tanks. A

A primary objectof our invention is to provide a. method of increasing recovery of petroleum oils from partially depleted oil bearing reservoirs and of storing hydrocarbons in these reservoirs during and after the recovery of the residual oil. p

Another object of `our invention is to provide a method of increasing the 'recovery of 'petroleum oils from partially depleted reservoirs by injecting condensible hydrocarbonl vapors into the reservoir, allowing said vapors to condense to form a solvent which mixes` with and reduces the viscosity and the surface tension of the hydrocarbon oil. thus facilitating drainagel of the hydrocarbon fluid mixture from the formation into a well bore.

Still another object ofl our invention is the provision of a method of injectingintofa-reservolr a solvent in vapor stateand recovering the solvent in a liquid state togethen-with dissolved reservoir oil.

Another object of our invention is to provide formation contains a string of oil well casing I4 which is sealed at the top by ra closure l5. Each closure supports a string of pump tubing I6, which conveys hydrocarbon oil from vthe bottom of the well bore to the surface vof the ground. Reciprocating pumps I1 are provided in the lower portion of the tubing strings and are employed to lift the hydrocarbon uid upwardly through .the tubing. It is to be understood that any type of pumping equipment which can be used successfully may be employed in the practice of our invention. Pumps I1, which are shown for purposes of description, are actuated by a string of sucker rods I8 which are reciprocated by any well known pumping equipment (not shown) at the surface of the ground. An annular space I9 is formed between the interior wall of the casing and the exterior wall of the tubing of eachof the aforementioned well bores. At the surface of theA ground we have shown a known type of still 20 which is connected to one or more distilling columns 2| by an intercommunicating conduit 22.

VStill 20 also communicates with tubing I6 through a crude loil deliveryline 23 and branch lines 24. Distillation of hydrocarbon liquid takes place in the still and distilling column, producing liquid fractions and a vapor fraction. The liquid fractions are drawnoff from the still andthe distilling column through llquidoutlets 25 and 3|, respectively, which convey the liquid fractions to desired disposal or storage apparatus (not shown). chiefly of butane with a desired amount of propane and smaller percentages of pentane and heavier hydrocarbons, is drawn off fromv the distillingcolumn by a conduit 26. It is to be understoodthat the components of the vapor fraction may be varied from time to time in order to facilitate the condensation of the vapor fraction which is injected into the reservoir to form a hydrocarbon solvent. This solvent reduces the surface tension and viscosity of the hydrocarbon 4 oil in place in the reservoir, thereby facilitating drainage to the well bores. Conduit 26 is provided with branch conduitsl, which connect with closures I5 in a manner to allow communication with annular spaces I9. A by-pass 28, which communicates with a compressor 29, anda valve. 30 are preferably provided in conduit 26 so that the vapors withdrawn from one well may be compressed and injected into another well along with the vapor from the distilling equipment. For descriptive purposes, we have the compressor arranged to compress vapors from well I0, and in ject them into well Il, however, this isnot to be considered as a limitation. Neither is our invention to be limited to any number of well "'bores.

In the practice of our invention, the general arrangement of apparatus illustrated in Figure 1 may be used in carrying out the steps of our` method of secondary recovery and underground storage of hydrocarbon vapors'.v It will be noted The vapor fraction, which consists\ .ture to the well bore.

that' hydrocarbon oil from a reservoir may contain volumes of propane and butane which are equal to as much as ten percent of the total reservoir fluid. To initiate the process, let us use well I0 as an input-well for vapors coming from still 20 and distilling column 2|. Additional l'volumes of propane'and butane from an, outside source (not shown) may be supplied to and vaporized in the distilling equipment as required. This butane and propane'is added to the butane and propane which may be recovered from hydrocarbon oil until a desired volume of these materials is present in the formation. It may be desirable fromk time to time to add additional propane and butane from an outside source in order to ,compensate for the hydrocarbon oil withdrawn from the reservoir. The vaporsV evolved in the vdistillation process are conveyed from distilling a column 2| by conduit .26, valve 30 being open,

and branch conduit 21 to closure I! of well bore III where the vapor is injected into the reservoir through annular space I8. During the` vapor in'jection step it may be desirable notgto pump -liquid from weli III, however, we11Il4 maybev pumpedduring vapor injection into well III. It

is obvious that the composition of the vapor evolved in the distilling process may be so controlled in the distilling apparatus that the vapor will contain propanes, butanes, and any heavier lhydrocarbons asdesired. In initiating Vourinvention, it is frequently desirable to a have a vapor consisting of. small amountsy of hydrocarbons which are heavier than butane. e

It is a. well known physical law that a vapor gives off latent heat 'upon condensation to a liquid. As heat always travels from a hotebody to a cooler body, the heat of condensation of Vthe vapor used inthe practice of our. inventionv will warm the .formationin which condensation takes place. The .large portion of the heat `supplied to the formation will'be the latent heat of condensation of the vapor, since only little sensible heat is available. densation of injected vapor may occur in annular space I9, heating the casing Il and pump ,tubing I6. Finally, upon continued injection, the vapors will `reach the formation and become condensed` therein, warming the formation locally and thev contained petroleum oil. It is also knownthat heat lowers the resistance to flow or viscosityof a petroleum oil while the condensate of the` injected vapor is also less viscous and has a lower surface tension than the formation oil.A

`"I'he condensed vapor acts asa solvent and mixes with the formation oil increasing therteme perature thereof and of the formation.` Aportion of the injected vapor will be dissolved the formation oil resulting also in a rise in temperature. This` temperature increase combined with the solvent action ofthe condensed and `dissolved vapors lowers the surface tension and f decreases the viscosity of the oil materially theree byfacilitating drainage of the'oil-solvent mixabove step in our process takesy place in a small area initially, and spreadsrout vover `a greater portion of the formation as thel temperature of `the formation increases and the oil in the reservoir and condensed vapors are drained to the input well bore and produced therefrom.

By the condensation of the injected vapors, the latent heat of condensation will sufiiciently warm the formation in which condensation takes place so that continued condensation of the injected vapors will not yoccur in lthis immediate area.

Initially some con- It 'will be seenthat the- Hlhis warming then gof the formation to q area ofinjection I be directed to` another jection pressure ofthe y allows the process to Yremove the formation oil from `progressively further from thelpoint of initial vapor injection. "As the jupper portion of the formation is usuallythe more y completelydrained; the injected vapors' will condense inthe upper portion nrst. q Thus, the condensedvapors readily drain to the lower` POrtions mix with thehydrocarbon oil therein, assisting p `to the well bore. The mixture oi' oil and propanebutane solvent which accumulates in well bore ll is periodically removed by pump I 1 to the surface.`

and is"then passed to `sti1l`2|| through tubing I6, i by way of branch line 24 and line 21. The oil solvent `mixture isdistilled in still andfdisitillingzcolumn 2lV in-which theliquid fractions are drawn'on' through conduits 25 26, valve and line 21 is recycled in theheretofore mentionedmanner.` It is to be noted that asthe petroleum oilis removed fromformation I3 and distilled and the propane and lbutane therefrom recycled,v the proportionof these hydrocarbons inthe cycle and therefore in the reservoir, increases particularly in the immediate where the increaseis very great. `The injection of vapor'l may becontinued until essentially all-of `the residual oil has been rep and sL-rell spectively and .the vaporI fraction through line the drainage oi' the residual oil 0.

ent. `vapor injection and pressure oi' the rounding the well liveredto well bore injected vapor facilitates drainage to an'oii'set producing well. Atsuch time,` as deemed expeditowell bore Iugmay be dis- Y i continuedyf` Withno vapor being injected or x withdrawn from vvellhore Il, the temperature` vapor in the formation surbore,` :whichjhas been drained of hydrocarbonoil, may the'n be removedfromwell bore III and de- IIalong' with additional vapor lfrom the surface distillingequipment; This I is accomplished by 4and directinsfthe vapor through compressor 29.

closing valve Jilin conduit 2l -f frneiiquiu there' is at its equilibrium-boiling point driven out ,of Vthe .utilising some of Y por injection may be moved from the formation. immediately sur-` rounding well Ill.` and the condensation of vapors spreads over the formationto facilitate the drain-` age of the residual oil: to well bore Ill` or other well Vbores (not shown),` from which the condensed vapor and oil solution maybe recovered as a liquid i At such time as deemed expedient, theinjectionof vapors may well` or wells such as to well boretl I in themannerlsimilarto that distowell bore Ilias well as v versing the step,

at the former operating pressure.

It 1 is;v i therefore, in the conditiongof..` live oil originallyconthe stored heat `by evaporation; rate of pressure reduction, va-

inoved from another input well. It is to `be noted thatby injecting vapor from one of the wells,

advantageously. por from iirst onewell to another tially all ofthehydrocarbon oil has been removed closed in relation to well I0. When essentially v all `the oil has been -removed from the forma" tionby the recycling of the propane-butane vapors, the pores of the formation will be illled with ,the propane-butane in tane volumetric ratio.

`- `At this time thereservoir is prepared for and may be `utilized forstorage of thevapors already g presentin the formation@ By increasing the in- 1 vapor, additional volumes l of butane` or propane maybe injected into and stored in the formation. As thevapor stored in the `reservoir will be atsuperatmosphericpres-` sure, it may be recovered from theformation 'with the aid of its ownl the pressure'ofthe vapors in the reservoir is rei duced to atmospheric, the remaining vapors may,` be recovered by applying a partial'vacuumto'the formation.

any desired propane-bufrom the formation and the formationthus'prop-'j vapors alreadyl presentin the formation. and Ai'or i ybe 'injected into Y such additional vapors as m the formation for storage.

Referring mineures-for a description 'oranfother modification of ourxinventiom it will4 be vapor pressure. When It will be noted thatwhile we have described our method specifically with respect to one input well, any number of input wells may be usedjor injection of theqvapors as predicated bythe op-` erating conditions which may be peculiar to a equipment has removed the oil for a considerable i 1 distance back in the formation surrounding the to the time that the input well bore, but prior may be withdrawn and injected into `heretofore described. i.

tion is otherwise pressure of the oil in place is built value by the cyclic returning of volatile material,` I

produced, while solve inthe hydrocarbon oilin `the upper part ofthe formation, the liquid drains to the lower portion ofthe formation `and well bore, carrying with it oil titles `than would thence into the in greater. quanothex'wise drain v thereto, be-

cause theliquidhas reduced the `viscosity .and

surface tension of the oil as heretofore disclosed. 'I 'he method of "this i identical with the first. It` is to be lnoted that the vapora-bove the packers Well bore II in the manner It isemphasized that this 'is not essentially a pressure process. 0n the'l contrary, it isdesir` able that pressures in the sand be held reasonthe pores which have been' ably low so' that emptied of liquid may be filled with a minimum of vapor. It is a process in which the vapor up to/a higher largely derived from the oil being reaches equilibrium. l Vapor distilling equipment. Byire l moving vapor from well bore Illythesurroundis virtually converted intol `a still.

pores'byits own vapor. After `renewedwhile vapor is reheat of condensation `is used" t The alternate injection of vaand then ref may be carriedout until essen`` modification of ourinvenfrom LWell bore I0,\if desired.`

at the same time temperature is raised in thel zone of condensation.

Though -we have described 'I0 asan input'jwell and `Il as a pumping well, itis desirableto use all wells, atthe start, as inputwells.V The purthem and to raise the temperature, locally, so that l in Veffect the'diameter of the hole inthe sand is-A increased by` providing a 'larger' cross section of open sand through which drainage can occur.

l As will be obvious, the yprocess results in the production'flrst 'of theheavier hydrocarbons of the crude oil.. It, therefore, affords a means, to a, renery located near old producing sands ofthis type, foi-producing the heavier oils without the eonsequentzincrease in'gasoline'stocks and likewise a meansof storingv gasoline and lighter fractionsunder ground while using such storage asarecoverymeans.l f 1 L The underground temperature at the condensing point may bei` computed 'from knowledge' of the pressure, together with. analysis of the lvapor being injected and liquid! phase being pumped. It is desirable to .change the composition ofvapor being returned asfmore of the sand is exhausted by( the process, Aby the inclusion of more propane and even methane so that the exhausted pores may be iilledwi-th vvapor of high volatility; Then when recoveryl of oil is .considered economically complete, Vthe "composition ofur'apor returned should have beenlsom controlled lthat injected material then present in the 'sand should consist of` substantially nothing heavier 1v"than butane and, that chiefly present'as' vapor. The final termination of aproject-` consists otpumping down the liquid level tothe lowest point geologically and thenexhausting.v the vapor 'by vacuum pumps and using the stored heatoto evaporate liquid which wetsthelower part of the sand. 4

T he. process is best adapted to lenticular structures of high porosity and high permeabilityin which there is no Water drive.' In addition to recovering crude petroleum oil-Which otherwise` mightbe lost, a special'uti-lity of our invention lies in the storage or deferred'production of lightrhydrocarbons. Its use is Well adaptedv to reduce the, overproduction of motor fuelv inwinter'v when market Vdemand for furnace oil'is heavy andY to permit building up ofstocks of butane and propane underground pending, development of av synthet'i rubber industry, the cost of storage'of their vapor pressure;v

From, the foregoing'. it is believed that the many advantages obtainable bythe practice of these aboveground beingprohibitive because of the present invention will bev readily apparent tov persons skilled inthe art. Howeversince many changes maybe made in carrying outthe `above method without departing vfrom the scope of the invention, as dened bythe appended claims, it is intended that all matter contained herein shall be interpreted as illustrative and rather than in a limiting sense. Y

Weclaim': o l

'1. A method of preparing partiallyV depleted oil bearing formations forv volatile hydrocarbon y explanatory,

f storage including the steps of injecting condens-` ,pose of this is to cleanlv out the'v sand body near u age reservoir has :been

ible hydrocarbon .vapor consisting of propane and butane at substantially atmospheric temperature and at -am'aximum pressure only slightly higher than the vapor pressure 4of propane at` formation temperature into the partially depleted oil bearing' formation through an input welLIpermitting the Vinjected `vapor to condense substantially completely 'to7 a liquid within the pores of the formation thereby `fill/arming- Vand dissolving Y the oil to facilitatedrainage ofthe oilinto the input vwell bore and into adjacent wel1-bores, producing'the mixture of oil and fully condensed: vapor fromlthe input and. adjacent well,;bores,. fr'actionatinglthis mixture into a; crude oil bottoms and vthe lcond'ensible v, hydrocarbon 1 vaporzlr` recycling the vapor and producing vthescondeiised vapor and oil mixture until a suitably large'storessentially V- freed of`its crude oil'content.y f

2. A' method of lpreparir'ig partially'depleted'oll bearing formations for volatile, hydrocarbon storage `including the steps of` injectingcondensible hydrocarbon vapor consisting of propane 'and butaneI at substantiallyatmosphericl temperature y andat afmaximum pressure only slightly higher than the vapor preSSureoofpropane at 'formation temperature into the partially depleted oil bear-` ing formation through an input well, permitting the. injected vapor .to condense substantiallyv completely to aV liquid within-the pores'ofthe formation thereby warming and dissolving'the oil', reducing thepress'ure and permitting at least some of the dissolved solvent to vaporiz'e' to replace the oil-solvent 'solution by solvent vapor to facilitate drainage of the oil into the input Well bore and into adjacent Well bores, producing the mixture of oil andr condensedvapor from' g the :input and adjacent well bores, Afract-'ionating this mixture into a .crude oil bottoms and the n co'ntlensibleY hydrocarbon; vapor; recycling; the

'vapor andproducing the'` condensed vapor and oil mixture until .a suitably large` storage vreservoir has been essentially freedv of its crude oilg content.

,3. Aumethod of producing petroleum@ oil from A. partially depleted wells including the steps of in-VV jecting condensible hydrocarbon'vapors consisting essentiallyofl propane and: butane atgsub` stantially atmospheric temperature-'and at af maximum pressure only slightly higher than the* vapor pressureof propane at formation temperature into the partially depleted oil producing formation, permitting the injectedvapors to condense substantially completely within the pores ofthe formation thereby warming by ther avail--v able vheat of condensation the residual-crude oil and dissolving said residual oil, producing this mixture' of fully condensed propane and butane and petroleum oil, fractionatingthismixture into a crude oilibottoms'and a propane and butane'- vapor; and vrecycling the propane and butano I the partially depleted oil producing vapor Y into formation.

'c EDWARD BUDDRUS. SAMUEL c; vcaRNmnff 

